Patient Care Setting

Biography

Research

Multisensory Interaction and Adaptive Plasticity in Spatial Localization and Orientation.

The sensori-neural processes underlying our abilities to localize, track, and interact with a cluttered environment are crucial attributes of daily life, and are among the most fundamental tasks of the nervous system. The integration of multiple sensory inputs are required to guide spatial behaviors, ranging from mundane tasks such as reaching for objects to complex ones such as navigating to and from the workplace. These functions are also among the first (and often most subtle) to register problems after head trauma, neurological disease, and aging. The goal of our research is to understand how the brain integrates sensory inputs from the outside world (location and motion of visual and auditory targets) with those of the internal senses (vestibular and somatosensory depictions of orientation and motion of the body and its parts,) to achieve meaningful spatial perceptions and behaviors (eye, head and postural movements and reflexes). An equally important interest is how plastic neural mechanisms register errors and adaptively adjust performance in order to maintain proper spatial calibration across sensory modalities, or analogously, recover normal function after suffering pathologic loss. Finally, an important translational concern is how the neural degeneration of natural aging affects spatial behavior and plasticity. Recent experiments have addressed two intriguing areas of interest. One is understanding how the brain utilizes auditory and visual information about target location and motion in order to maintain accurate and congruent spatial calibration across modalities, as assessed through different forms of orienting movements ("pointing"). These include visually-guided manual pointing by laser joystick, and more natural gaze (eye and head) pointing. Since gaze shifts activate vestibular reflexes (vestibulo-ocular and –collic reflexes: VOR and VCR) as well as somatosensory feedback from the neck, we have addressed how the senses interact with each other and with volitional and reflex motor control. We also investigated the important challenges of spatial memory when targets are transient, as occurs frequently in nature. Finally, we maintain interest in how spatial sensory modalities are plastically co-calibrated by cross-sensory experience--an essential feature normal spatial behavior over a lifetime.

A second focus has addressed vestibular inputs during both angular (from the semicircular canals) and linear (from the otoliths) head motion and how they interact with each other, despite an intriguing limitation in the physics of the linear form (Einstein's "equivalency principle"). As biological linear accelerometers, the otolith organs cannot readily distinguish accelerations due to head tilt (relative to gravity) from those arising during translational (as opposed to angular) motion, and yet relevant behaviors and perceptions associated with these two forms of motion differ greatly.

The lab has completed a set of studies related to the above topics, and witnessed several graduate students through completion of PhD requirements. I have returned to largely a clinical role related to disorders of balance and equilibrium--a cross between neuro-otology and neuro-ophthalmology--and serve in an advisory role for students and others at all levels.